In this article we will discuss different ways to remove all elements from a set in python.
Remove all elements from a set using clear() function
In python, the Set class provides a function clear() that can empty a set i.e. delete all elements from the set. For example,
# Create a Set of numbers
set_of_num = {1, 2, 11, 6, 7, 4, 5, 6}
# Delete all elements in the set
set_of_num.clear()
print('Set Contents: ')
print(set_of_num)
Output
Set Contents: set()
To confirm, if all elements are deleted from the set or not, we can check the size of the set. For example,
# Check the size of list to confirm if all elements are deleted
print('Set Size: ', len(set_of_num))
Output:
Set Size: 0
Remove all elements from a set using difference_update()
In python, the Set class provides a function difference_update() that accepts a sequence as an argument and deletes all the elements in this sequence from the set. Let’s use this to remove all elements of the set,
# Set of numbers
set_of_num = {1, 2, 11, 6, 7, 4, 5, 6}
# Delete all elements of a set from the same set | Empty a set
set_of_num.difference_update(set_of_num)
print('Set Contents: ')
print(set_of_num)
Output:
Set Contents: set()
We passed the same set object as an argument in the difference_update(), so it deleted all elements of the set.
To confirm, if all elements are deleted from the set or not, we can check the size of the set. For example,
# Check the size of list to confirm if all elements are deleted
print('Set Size: ', len(set_of_num))
Output:
Set Size: 0
Remove all elements from a set while iterating using for loop and discard()
If we iterate over a set and try to remove each element while iteration, then it will raise error,
# Set of numbers
set_of_num = {1, 2, 11, 6, 7, 4, 5, 6}
# RuntimeError: Set changed size during iteration
for elem in set_of_num:
set_of_num.discard(elem)
Error
RuntimeError: Set changed size during iteration
It is because we can not modify a set while iterating over it.
So, we will create a list of the set elements, then iterate over that list and for each element, we will delete it from the set,
# Set of numbers
set_of_num = {1, 2, 11, 6, 7, 4, 5, 6}
# Iterate over the elements of set (by converting it to a list)
for elem in list(set_of_num):
# Remove each element
set_of_num.discard(elem)
print('Set Contents: ')
print(set_of_num)
Output:
Set Contents: set()
To confirm, if all elements are deleted from the set or not, we can check the size of the set. For example,
# Check the size of list to confirm if all elements are deleted
print('Set Size: ', len(set_of_num))
Output:
Set Size: 0
It seems to be an overkill for the small job of just clearing a set, but this solution can be useful if you want to delete some specific elements from the set, while iterating over the set.
The complete example is as follows,
def main():
print('*** Remove all elements from a set using clear() function ***')
# Set of numbers
set_of_num = {1, 2, 11, 6, 7, 4, 5, 6}
print('Set Contents: ')
print(set_of_num)
# Delete all elements in the set
set_of_num.clear()
print('Set Contents: ')
print(set_of_num)
# Check the size of list to confirm if all elements are deleted
print('Set Size: ', len(set_of_num))
print('*** Remove all elements from a set using difference_update() ***')
# Set of numbers
set_of_num = {1, 2, 11, 6, 7, 4, 5, 6}
# Delete all elements of a set from the same set | Empty a set
set_of_num.difference_update(set_of_num)
print('Set Contents: ')
print(set_of_num)
# Check the size of list to confirm if all elements are deleted
print('Set Size: ', len(set_of_num))
print('*** Remove all elements from a set using for loop and discard() ***')
# Set of numbers
set_of_num = {1, 2, 11, 6, 7, 4, 5, 6}
# RuntimeError: Set changed size during iteration
'''
for elem in set_of_num:
set_of_num.discard(elem)
'''
# Iterate over the elements of set (by converting it to a list)
for elem in list(set_of_num):
# Remove each element
set_of_num.discard(elem)
print('Set Contents: ')
print(set_of_num)
# Check the size of list to confirm if all elements are deleted
print('Set Size: ', len(set_of_num))
if __name__ == '__main__':
main()
Output:
*** Remove all elements from a set using clear() function ***
Set Contents:
{1, 2, 4, 5, 6, 7, 11}
Set Contents:
set()
Set Size: 0
*** Remove all elements from a set using difference_update() ***
Set Contents:
set()
Set Size: 0
*** Remove all elements from a set using for loop and discard() ***
Set Contents:
set()
Set Size: 0